Advances in camera and display technology enable images (including both still images and video content) to be captured and displayed with improved precision and greater dynamic range than before. For example, as compared with images captured by older cameras, newer cameras may capture images having:                larger color gamut;        greater absolute luminance range (e.g., the range of luminances that can be recorded as distinct values before saturation);        greater contrast ratio;        greater resolution;        more precise output signal formats;        greater color depth;        greater luminance depth;        etc.Similarly, as compared with images displayed on older displays, images displayed on newer displays may have:        larger color gamut;        greater absolute luminance range (e.g., greater maximum brightness);        greater contrast ratio;        greater resolution;        greater color depth;        greater luminance depth;        etc.        
The rapidity with which advances in camera and display technology occur and the vagaries with which these advances are adopted may lead to the situation where video content is captured by cameras that are less capable than displays on which it is desired to display the video content. Conversely, it may occur that video content is captured by cameras that are more capable than display on which it is desired to display the video content. In either case, it may desirable to adjust the video content so that it better conforms to the capabilities of the displays (e.g., by expanding or shrinking color gamut, dynamic range, etc.).
The creator of a video production or other image may set tones and colors of pixels in the image so that, when viewed, the image has a desired appearance which agrees with the creator's creative intent. Adjusting tones and colors of pixels in an image may include performing color grading (or ‘color timing’) on the source video data. Color grading may be performed using a hardware/software system (sometimes referred to as a color grading station) that permits a user (sometimes referred to as a color grader or colorist) to change the video data in various ways to achieve a desired appearance. Color grading may involve manual user input (e.g., in the case of pre-recorded video productions) or may be performed automatically according to pre-determined parameters (e.g., in the case of live broadcasts).
Color grading may be used to adjust the video content to fit more or less capable displays. Where there is a mismatch between the capabilities of a camera used to capture video content and the display used in color grading, it may be difficult and/or time consuming to adjust the video content to fit the capabilities of the display using existing color grading tools. Color grading video content captured by more capable cameras using existing color grading tools may be difficult even where the capabilities of the cameras and displays are not mismatched. For example, offset, gain, gamma adjustments heretofore used in color grading may provide less intuitive control and yield less satisfactory results in the context of video content having high dynamic range (the term “high dynamic range” means dynamic ranges of 800:1 or more) or relatively high maximum luminance (e.g., maximum luminance greater than 1000 nits).
Similar difficulties may be encountered when video content color graded for display on one display (e.g., a reference display) is subsequently color graded for display on a different display (e.g., a target display).
Accordingly, there is a desire for improved color grading methods and apparatus.